Spinal cord injury (SCI) is a complex and heterogeneous condition. This means no two injuries are alike. SCI occurs when trauma (such as a fall, sport injury, or vehicle accident) or disease (such as a tumor, infection, or spina bifida) damages the spinal cord, resulting in loss of sensation and/or muscle function.
Signs and symptoms of SCI vary depending on injury type and the individual who sustained the SCI. Early symptoms often include spinal shock and neurogenic shock. Long-term symptoms may include changes in sensation, muscle control, spasticity, breathing difficulties, bladder and bowel dysfunction and autonomic dysreflexia.
SCI can have profound and varied impacts on an individual’s physical function and quality of life, depending largely on the nature and severity of the injury. These injuries are generally categorized into two main types: complete and incomplete. Understanding the distinction between these types is crucial for both medical professionals and those affected by SCI, as it influences prognosis, treatment strategies, and rehabilitation outcomes.
Complete Spinal Cord Injury:
- In a complete SCI, there is a total loss of motor and sensory function below the level of injury. However, in certain instances, individuals with complete SCI can still retain some strength or sensation in areas below the injury site.
- There is no voluntary movement or sensory perception in the affected areas, including crucial functions like bladder and bowel control, which are governed by the lowest segments of the spinal cord.
Incomplete Spinal Cord Injury:
An incomplete SCI involves some preserved motor or sensory function below the level of injury, including bladder and bowel function.
Symptoms of incomplete injuries vary widely and can be categorized into several syndromes based on the affected area of the spinal cord:
- Central Cord Syndrome: Typically affects the cervical spine, resulting in greater weakness in the arms than in the legs.
- Brown-Séquard Syndrome: Involves injury to one side of the spinal cord, leading to weakness and loss of joint position sense on the same side, and loss of pain and temperature sensation on the opposite side.
- Conus Medullaris Syndrome: Affects the conus medullaris (the end of the spinal cord), causing loss of bladder and bowel control and variable leg function.
- Cauda Equina Syndrome: Involves injury to the cauda equina (the bundle of nerves at the end of the spinal cord), leading to loss of bladder, bowel control, and reflexes in the legs.
Pathophysiology / Anatomy of the Spinal Cord
The spinal column consists of 33 vertebrae – rings of bone that surround and protect the spinal cord. These vertebrae are divided into five segments: cervical, thoracic, lumbar, sacral, and coccygeal.
Tetraplegia, often referred to as quadriplegia, occurs when a spinal cord injury affects the cervical (neck) region of the spinal cord. This results in a partial or complete loss of strength and sensation in the neck, trunk, arms and legs. Individuals with tetraplegia may experience paralysis or weakness in all four limbs, as well as potential loss of function in other areas of the body, depending on the severity of the injury.
Paraplegia, on the other hand, occurs when a spinal cord injury affects the thoracic, lumbar, or sacral regions of the spinal cord. This leads to a partial or complete loss of strength and sensation in the lower half of the body, including the legs and trunk, while the arms remain unaffected. People with paraplegia typically experience paralysis or weakness in the lower limbs, but they retain normal function in their arms and upper body.
The upper seven vertebrae are located in the neck. The nerves in this area control head and neck movement, the diaphragm, deltoids, biceps and muscles controlling the wrist and hands.
C1 – C3: Injury to the C1, C2 and C3 sections of the spinal cord typically results in loss of function to the neck and below, including loss of diaphragm function which necessitates a ventilator for breathing.
C4: Significant loss of function at the shoulders and below.
C5: Potential loss of functions in shoulders and biceps, complete loss of function below.
C6: Limited wrist control and loss of much hand function.
C7: Use of arms is retained, but results in a lack of hand dexterity.
The 12 vertebrae that extend through the chest area. Arm and hand function is unaffected.
T1 – T8: Trunk stability is affected by the inability to control abdominal muscles. The higher the injury, the more severe the effects. Some impairment of respiratory muscle function is also seen due to loss of use of the intercostal muscles that move the ribs.
T9 – T12: Results in variable loss of trunk and abdominal muscle control.
The 5 vertebrae in the lower back. Injury to this area damages the very lowermost tip of the spinal cord or the cauda equine which results in decreased control of hips and legs, as well as bladder, bowel and sexual function.
The 5 vertebrae are located in the pelvic area. As with lumbar injuries, damage to the sacral nerves can result in decreased control of hips, legs, bladder, bowel and sexual function.
Four fused vertebrae commonly referred to as the tailbone. An injury to the coccyx is not associated with any significant loss of nerve function.
When considering the anatomy of the spinal cord we also need to consider myotomes and dermatomes. Myotomes represent specific muscle groups controlled by the same nerve root while dermatomes represent specific areas of skin sensation supplied by a particular nerve root.
When there is an SCI, the conduction of sensory and motor signals across the site(s) of the lesion(s) is disrupted. This disruption can affect both sensory perception and muscle control. By systematically examining both dermatomes and myotomes, clinicians can determine which spinal cord segments are affected by the SCI.
C5: Shoulder abduction
C6: Elbow flexion and wrist extension
C7: Elbow extension
C8 (not a vertebra but a nerve root): Thumb extension, ulnar deviation
T1: Finger abduction
L2: Hip flexion
L3: Knee extension
L4: Ankle dorsiflexion
L5: Big toe extension
S1: Ankle plantarflexion
S2: Knee flexion
Cervical [AK2]
C2: Crown of the head, posterior scalp, earlobes, lower jaw
C3: Base of the skull, upper neck
C4: Lower neck, upper shoulders
C5: Clavicle
C6: Thumb
C7: Index finger, middle finger
C8: Little finger, ring finger
Thoracic Dermatomes
T1: Upper chest and back, axilla, upper medial arm
T2, T3: Upper chest and back
T4: Level of nipples
T6: Xiphoid process
T10: Umbilicus
L1: Groin, greater trochanter, lower back
L2, L3: Lower back, hips, anterior and inner thighs
L3: Medial knee
L4: Lower back, anterior thigh, anterior knee, medial calf, medial ankle, medial aspect of the great toe
L5: Lower back, anterior and lateral shin, lateral aspect of the great toe and second-fourth toes, top and bottom of the foot along 2-4 toes
S1: Buttock, posterolateral leg, little toe
S2: Buttock, genitals, posteromedial leg
S3: Buttock, genitals
S2-S4: Perineum
S5: anus
Levels of Injury
Neurological Level of Injury
The neurological level of injury refers to the lowest segment of the spinal cord with normal sensory and motor function on both sides of the body. Determining this level is crucial for assessing the extent of impairment caused by an SCI.
ASIA Impairment Scale (AIS)
The ASIA Impairment Scale (AIS) is a classification system used to categorize the severity and completeness of an SCI. It grades injuries from A to E:
- Grade A: Complete loss of sensory and motor function below the level of injury.
- Grade B: Some sensory function preserved, but no motor function below the level of injury.
- Grade C: Some motor function preserved, with more than half of the key muscles below the level of injury having a muscle grade less than 3.
- Grade D: Some motor function preserved, with at least half of the key muscles below the level of injury having a muscle grade of 3 or higher.
- Grade E: Normal motor and sensory function.
These classifications aid in predicting recovery outcomes, guiding treatment plans, and assessing interventions for individuals with SCI.
PLEX Engagement and IKT
Meaningful and effective engagement occurs when PLEX have an active role in decision-making, setting priorities, conducting research, and translating research knowledge. This requires an inclusive environment with supports that allow PLEX to fully contribute and be part of mutually respectful teams from the start of projects.